Trinh Vu-Duc

Impact of thermal proofing of a church on its indoor air quality: The combustion of candles and incense as a source of pollution

Some years ago, a parish in Geneva decided to reduce heating costs by insulating its church to make it more energy efficient. Three years after the last renovations, it was observed that the internal surfaces of the naves had already become dusty compared with the customary frequency of 10–12 years. Dust even deposited on various surfaces during religious services. Our investigation showed that nearly all the dust found inside the church may in fact be soot from incense and candle combustion. Incense appears to be a significant source of polycyclic aromatic hydrocarbons. With a mechanical ventilation system and petrol lamps resembling candles the problem can be resolved.

Design and evaluation of a solid sampler for the monitoring of airborne 1,6-hexamethylene diisocyanate (HDI) and its prepolymers in two-component spray painting

An active, solvent-free solid sampler was developed for the collection of 1,6-hexamethylene diisocyanate (HDI) aerosol and prepolymers. The sampler was made of a filter impregnated with 1-(2-methoxyphenyl)piperazine contained in a filter holder. Interferences with HDI were observed when a set of cellulose acetate filters and a polystyrene filter holder were used; a glass fiber filter and polypropylene filter cassette gave better results. The applicability of the sampling and analytical procedure was validated with a test chamber, constructed for the dynamic generation of HDI aerosol and prepolymers in commercial two-component spray paints (Desmodur N75) used in car refinishing. The particle size distribution, temporal stability, and spatial uniformity of the simulated aerosol were established in order to test the sampler. The monitoring of aerosol concentrations was conducted with the solid sampler paired to the reference impinger technique (impinger flasks contained 10 mL of 0.5 mg/mL 1-(2-methoxyphenyl)piperazine in toluene) under a controlled atmosphere in the test chamber. Analyses of derivatized HDI and prepolymers were carried out by using high-performance liquid chromatography and ultraviolet detection. The correlation between the solvent-free and the impinger techniques appeared fairly good (Y = 0.979X-0.161; R = 0.978), when the tests were conducted in the range of 0.1 to 10 times the threshold limit value (TLV) for HDI monomer and up to 60 micrograms/m3 (3 U.K. TLVs) for total -N=C=O groups.

Performance of a chromatographic procedure used in the certification of reference material for polycyclic aromatic hydrocarbons in sewage sludge

Semi-automatic capillary gas chromatographic method with classical flame ionization detection, which satisfies the conditions for required performance and gave acceptable results within the framework of an interlaboratory certification programme for PAHs in sewage sludge, is described. The interesting feature of the procedure is that it incorporates automatic operations such as sample fractionation by semi-preparative HPLC, fraction collection at signal level recognition and evaporation under nitrogen flow. Multiple injections in the GC capillary column are performed in the on-column mode via an autosampler with temperature-programmable injector. Automatic data acquisition and chromatogram treatment are made via computer software. This partially automatic procedure releases personnel from tedious and time-consuming tasks and its robust character was validated through the certification of reference material for PAHs in sewage sludge, demonstrating its reliable performance.

Sidestream tobacco smoke constituents in indoor air modelled in an experimental chamber— Polycyclic aromatic hydrocarbons

Exposure to sidestream tobacco smoke is concerned with constituents in suspension in the indoor atmosphere. The natural dissipation of sidestream tobacco smoke has been investigated in a static atmosphere in a 10 m3 experimental chamber, and the rate of dissipation is expressed as T0.5, the half-life of residence in the air. Respective T0.5 of smoke components are calculated from the various sample data points, assuming a kinetic equation of the first-order process. Sidestream smoke has been generated by a smoking machine according to the Coresta standard protocol and then left to age over an 8-hour period, with subsequent sampling at defined time intervals. The experiments have been repeated over five days, and eight data point samples are obtained for each experiment. Besides nicotine, CO, and smoke particulate matter, interest has been focused on polycyclic aromatic hydrocarbons (PAH). The initial concentrations, C0 for smoke particulate matter and nicotine (gas and particulate phases) are found to be 13.8 mg and 92 μg per cigarette per cubic meter, with T0.5 being 2.6 and 2.1 hours, respectively. Low molecular-weight PAH have T0.5 up to 20 hours, explainable only by their high concentrations in the gas phase, while the 3- to 7-ring PAH have T0.5 of about 2 hours. The contribution of CO to ambient concentration is 91 mg per cigarette per cubic meter. The data can be useful in mathematical modellization studies regarding ventilation or exposure to sidestream smoke.

Laboratory Generated Bitumen Fumes Under Standardized Conditions. Clean-up Scheme and Ion Trap GC-MS Analysis of VOC, Semi-Volatile and Particulate PAH and PASH

This article reports the applicability of an efficient clean-up and enrichment procedure for the determination of polycyclic aromatic compounds (PAC) including polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulfur heterocyclic hydrocarbons (PASH) in the gas and particulate phases in raw bitumen and bitumen fumes by gas chromatography-ion trap mass spectrometry. The scheme includes a liquid-liquid partition to eliminate the aliphatics, a solid phase extraction on SiO2 cartridge to remove the polar compounds and an HPLC fractionation to isolate the aromatic fraction. The purified extract enables the determination of PAH profile from 2 to 7 rings including their methyl derivatives and 3 carcinogenic benzonaphthothiophene isomers. The reproducibility of the method was estimated by analyzing 6 bitumen replicates and is around the 30% overall uncertainty or less. In bitumen fumes generated at 170°C under standardized conditions, VOC and semi-volatile PAH were sampled with XAD-2 tubes and were also determined in six replicates. The VOCs are mainly monoaromatic derivatives (4% of fumes) and aliphatics essentially from C6 to C17 (27%). With regards to the particulate phase PAC, the coefficients of variation from 6 replicates are 5–24% for PAH and 6–10% for PASH. Data on VOC and PASH represent new contribution in the characterization of bitumen fumes.

Asthme professionnel dû aux isocyanates: Nouvelles orientations des recherches en hygiène du travail

The replacement of the HDI monomer by less volatile prepolymers is not accompanied by a decrease of the incidence of occupational asthma in Switzerland. Field measurements show that the prepolymer concentration levels may be high although the monomer is hardly detectable or complies with the norm. Our researches are focused on the improvement of generation and measurement techniques (international quality control), on the characterization of the prepolymers to study their transformation in biological media. Field surveys will be conducted to establish the prepolymer concentration profiles. We recommend for the introduction in Switzerland of threshold limit values for HDI-biuret and isocyanurate.